1. Field of Invention
The present invention relates to a lamp, and more particularly to a high pressure sodium lamp comprising a sodium vapor illumination arrangement which is capable of generating light which has more than 1500 W power.
2. Description of Related Arts
A conventional high pressure sodium lamp usually comprises a threaded head for externally connecting to a power source, a glass housing provided on the threaded head, and an arc tube mounted on the glass housing and filled with a predetermined amount of sodium vapor and/or other gases so that when the threaded head is electrically connected to the external power source, the sodium vapor in the arc tube is excited to generate illumination.
This conventional high pressure sodium lamp has the established advantages of having high efficiency, low energy consumption, enhanced product life span and capable of providing high intensity illumination. Because of these advantages, conventional high pressure sodium lamp has widely been used all over the world. A major disadvantage of the above-mentioned high pressure sodium lamp is that almost all high pressure sodium lamp has less than 1000 W power. As a result, its application is severely limited because many applications require high intensity of illumination which exceeds 1000 W.
One of the major reasons limiting the power of convention high pressure sodium lamp is that when the power of the conventional sodium lamp exceeds 1000 W, the lamp will generate a substantial amount of heat and it will cause overheat problem to the physical components of the high pressure sodium lamp. Moreover, when the power of the sodium lamp is increased, the overall size of which will also be increased and this will present a new limitation on the application of the sodium lamp. For example, when the overall size of the high pressure sodium lamp is too bulky, it may not be suitable to use in particular circumstances even though it can generate a substantial intensity of illumination.